Method for operating a drive train having a hydrodynamic clutch

ABSTRACT

A method for operating a drive train by providing a primary drive machine, a working machine, a hydrodynamic clutch, and a temperature detection device; wherein at least in the case of a change from a load state and/or an operating state of the drive train thereby creating a new load state and a new operational state, the temperature of the hydrodynamic clutch is detected at the time of the change; wherein on the basis of the detected temperature and the new load state and/or the new operational state of the drive train, an expected temperature progression is calculated; and wherein a warning signal and/or a stop signal is issued for the primary drive machine if a temperature of the calculated temperature progression exceeds a predetermined maximum temperature within the expected duration of the new load state and/or the new operational state.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2014/067748,entitled “METHOD FOR OPERATING A DRIVE TRAIN HAVING A HYDRODYNAMICCLUTCH”, filed Aug. 20, 2014, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for operating a drive train having ahydrodynamic clutch, or respectively a turbo clutch.

2. Description of the Related Art

A drive train is known from the current state of the art. It consiststypically of a primary drive machine that drives a working machine via ahydrodynamic clutch. It can be used for example in the field ofindustrial drive applications, in particular for driving of materialconveyors, crushers, or similar applications.

A hydrodynamic clutch or respectively turbo clutch that can be driven inthe drive train is known for example from DE 10 2004 006 358 B4. Theturbo clutch described therein features a contactless temperaturemeasuring device, so that above a predetermined maximum temperature, theprimary drive machine that drives the working machine by way of theclutch is reduced in its efficiency or is in particular shut off.

The advantage when utilizing a contactless thermal measuring deviceaccording to the aforementioned German patent document is in particular,that the temperature measurement occurs directly in the operating mediumand therefore temperature changes that always accompany load changes inthe drive train can be very quickly recognized. Based on this directavailability of the temperature values and load states accompanyingsame, it becomes possible in particular, to accordingly warn theoperator in various warning stages, so that the operator can reduce orcompletely eliminate the load before a thermal overload of thehydrodynamic clutch occurs.

A basic problem remains, however. For the event of dynamic changes ofoperating states or load states, in particular when the system had to beshut off due to a thermal overload of the hydrodynamic clutch, there isthe danger that, in the event of a new start of the system a thermaloverload occurs again very quickly, since a start of the line is alwaysconnected with a corresponding temperature rise in the hydraulic clutch.This temperature increase that occurs typically at the start can—inparticular with a not yet sufficiently cooled off system—ensure thatafter the start an emergency shut-off occurs again very quickly, becausea thermal overload of the hydrodynamic clutch occurs again. Thispresents a considerable disadvantage for the system user.

It is therefore the objective of the current invention to cite a methodthat improves the operation of a generic drive train and that, inparticular avoids the aforementioned disadvantage.

SUMMARY OF THE INVENTION

It is now provided in the method according to the invention that—atleast in the event of a change in the load state and/or operating stateof the drive train—the temperature is detected via a temperaturedetection device. An expected temperature progression is then calculatedon the basis of this detected temperature, as well as with the knowledgeof the new load state, or respectively operating state of the drivetrain. This calculation or simulation of an expected temperatureprogression can then be used to issue a warning or stop signal for theprimary drive machine if the temperature of the calculated temperatureprogression exceeds a predefined maximum temperature within the expectedduration of the new load state and/or the new operating state.

The temperature control for the drive train is thus equipped with acertain “intelligence”. The system is not stopped as was the casehitherto, based merely on exceeding a critical temperature. Rather, aprojection of the expected temperature change is calculated always whena dynamic change occurs; for example when changing from a stopped stateinto a startup procedure, at the change from a startup procedure intothe regular operation, the change from regular operation with load 1 toregular operation with load 2, and so on. In this projection of theexpected temperature change the new state is included, in other wordsfor example a startup state with the projected load at the time ofshut-off, or in the event of a load change, the increased load.

As long as the calculated temperature progression remains below apredefined maximum temperature of the hydrodynamic clutch, nointervention occurs. If it approaches such a temperature, a warningsignal may for example be issued that prompts the system user to, forexample reduce the load. Only when it becomes clear that the maximumtemperature of the calculated temperature progression will for certainexceed the maximum permissible temperature of the turbo clutch, a stopsignal is triggered and the drive train is stopped.

In an additional very favorable arrangement of the method according tothe invention it can moreover be provided that a warning signal and/or astop signal for the primary drive machine is issued when the currenttemperature becomes greater than the corresponding value of thecalculated temperature progression. Not only the projection and thereaction to the expected maximum temperature is possible with the methodaccording to the invention. Rather, it is now possible to also track towhat extent the behavior of the hydrodynamic clutch that is measurableby way of the current temperature is consistent with the projectedtemperature behavior. If this is the case—and there is always a certainsafety distance between the values—no action is undertaken. If this isnot the case and the current measured temperature value exceeds forexample the projected temperature progression, then typically a faultoccurs, for example a blockage of the drive train during the startupprocess. This can then be detected extraordinarily quickly and used togenerate a warning signal or in particular a stop signal for the primarydrive machine.

For the case of a change of the operating state from a turned on to ashut off state of the primary drive machine, it can now be provided inan additional exceptional arrangement of the method according to theinvention that, based on the load state at the time of the shut-off,additionally a start-up temperature progression of a warm-up in theevent of a start of the drive train is calculated. From this simulationof the temperature progression during the repeated start-up of the drivetrain under the same load that existed at the time of the stop, amaximum start-up temperature difference by which the drive train heatsup in the event of a start-up can then be determined. Now, one can waitbefore release of a renewed start of the drive train until thecalculated temperature progression of cooling has reached a releasetemperature that falls below the maximum temperature by at least thestartup temperature.

This ensures that the hydrodynamic clutch is in a position to absorb thecomplete temperature increase that occurs during start-up, withoutthereby exceeding the maximum permitted operating temperature and tocause, for example, an emergency stop. The problem described at thebeginning can thus be countered effectively.

It is thus possible that reaching the release temperature occurs by wayof a comparison of the respectively current detected temperature withthe corresponding value of the calculated temperature progression. Analternative thereto is also conceivable, wherein reaching the releasetemperature is monitored by a time counter. For this purpose, a timecounter is started when shutting down the drive train. One then waitsuntil the time counter has reached a time value that permits renewedstarting, whereby the hydrodynamic clutch is cooled to a point that thestartup temperature difference of the hydrodynamic clutch can again bedetected. On the one hand this can occur through the already describedsimulation in such a way that the time value that has to be reached bythe time counter is predefined by the temperature progression, namely asthe time value at which the release temperature is reached. Analternative exists in accordingly predefining the time value—independentof such a calculation—by way of characteristic diagrams or respectivelycharacteristic curves, subject to the temperature at the time ofshut-off, as well the load of the drive machine.

If it is known for example from simulation or experience that with apredetermined load, the drive train heats during startup in the area ofthe hydrodynamic clutch by a temperature value of 50 K then, on thebasis of the temperature at which the primary drive machine is shut off,a cool-down had to occur that led to a temperature value at least 50Kbelow the maximum permissible operating temperature. Only then is therelease signal set and the drive train restarted.

According to a very advantageous further development of the inventivemethod it may moreover be provided that, in a calculation of thetemperature progression, the ambient temperature of the hydrodynamiccomponent is considered. This is of decisive importance in particularfor the cooling behavior of the hydrodynamic clutch, in other words fora dynamic change from operation into shut-off state, since it plays adecisive role in the cooling behavior and thus in determination of therelease temperature, or respectively the duration until releasetemperature.

In an additional very favorable arrangement it may moreover be providedthat the current temperature that is detected by the temperaturedetection device is corrected with a temperature value, subject to theoccurring temperature gradient. Temperature measurements are frequentlyaffected by a certain time delay. This applies also to the temperaturemeasurement inside a hydrodynamic clutch, since the maximum temperaturedoes not adjust itself at the time at which it was measured, buttypically already before. Subject to the temperature gradient, thedetected temperature value can therefore be corrected, thus improvingthe accuracy of the operating procedure. In one advantageous furtherdevelopment of this concept it is thus provided that the correctionvalue progresses proportionally to the temperature gradient, since amore rapidly changing temperature requires a higher correction value.

In an additional very favorable arrangement of the inventive method itcan now moreover be provided that, as of a maximum operating temperaturethe load on the hydrodynamic clutch is reduced by a decrease in a drivepower and/or a load, wherein the maximum operating temperature is lessthan the maximum temperature. In this especially favorable andadvantageous advancement a maximum operating temperature can bepredefined, as of which a further temperature increase is countered witha decrease in the drive power and/or the load in order to avoid, ifpossible, an unnecessary shut-off and thereby an unnecessary down timeof the drive train. In an additional very favorable arrangement of thisconcept it can now moreover be provided that a complete reduction of theload occurs at a warning temperature that is predefined greater than themaximum operating temperature and lower than the maximum temperature.With such a load reduction, a further temperature increase can bemeaningfully countered. An emergency shut-off of the system due toexceeding the maximum temperature can thus possibly also be avoided,contributing in turn to an improved uptime of the drive train.

In an additional very advantageous arrangement thereof it may moreoverbe provided that the hydrodynamic clutch is protected by a fusiblesafety plug that is designed for a temperature above the maximumtemperature. Such a fusible safety plug as is known for example for thecurrent state of the art can be provided in any event. The fusiblesafety plug is ideally designed for a temperature value above themaximum temperature, so that in a meaningful functionality of theinventive method, it typically does not respond. It will only respond ifthe inventive method fails, for example if individual measured valuescannot be detected, if the energy supply fails, or if other similarcircumstances occur. At a temperature above the maximum temperature aseparation of drive machine and working machine in the drive train isforced in this case by way of melting of the fusible safety plug and atherewith associated release of the working medium from the hydrodynamicclutch.

As already mentioned, the measurement of the temperature in thehydrodynamic clutch can occur via a measurement in the hydrodynamicclutch and a contactless transfer of the measured value into astationary analysis unit. This structure, analogous to the German patentmentioned in the beginning is especially simple and efficient, since itcan detect the temperature values in the hydrodynamic clutch orrespectively in the working medium located in the hydrodynamic clutchvery directly and exceptionally quickly. The hydrodynamic clutch may inprinciple be any type of hydrodynamic clutch—for example a hydrodynamicconverter or, in particular also a hydrodynamic clutch or respectively aturbo clutch.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawing, wherein:

FIG. 1 illustrates a drive train according to the invention, with ahydrodynamic clutch, in particular a turbo clutch with which theinventive method can be realized;

FIG. 2 is a simplified flow chart for the inventive method;

FIGS. 3A-D are the flow charts according to FIG. 2 in one possibledetailed arrangement;

FIG. 4 is a diagram showing the simulation of a run-up of the drivetrain; and

FIG. 5 is a diagram showing the simulation of the cooling behavior ofthe drive train.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

The illustration in FIG. 1 is a highly schematized and merely exemplaryillustration of a drive train. Drive train 1 is structured in such amanner that it includes a hydrodynamic clutch 2, in particular a turboclutch (VTK). A working machine 5 is driven via a primary drive machinethrough an indicated transmission 4, wherein turbo clutch 2 can be partof this transmission 4 or can be an independent component in addition toa suchlike transmission, or is used in place of such a transmission 4.Working machine 5 may for example be a working machine 5 in thestationary region, in particular a material conveyor, a shredder or asimilar machine. Turbo clutch 2 includes a contactless thermal measuringdevice 6 in the region of turbo clutch 2. Contactless thermal measuringdevice (BTM) 6 corresponds with a receiver 7 that is in correspondingcontact with an analysis device (AWG) 8 or is part of such. Atemperature signal that is sent by contactless measuring device 6 isaccordingly evaluated by analysis device 8, and activation of primarydrive machine 3, in particular of an electric motor can in particularoccur. This is accordingly indicated by the arrows between analysisdevice 8 and primary drive machine 3. Analysis device 8 can at the sametime receive signals from the outside, for example a start signal, orthe like. This is indicated accordingly by double arrow 9. The oppositedirection of double arrow 9 is meant to indicate that signals ofanalysis device 8 can be issued to the outside, for example warningsignals of exceeding a predetermined temperature, or the like.

In the schematic diagram in FIG. 1 a fusible safety plug (SSS) 20 ismoreover illustrated in the region of turbo clutch 2. This is generallyknown from the current state of the art and represents a final safetydevice that prevents overheating of turbo clutch 2 in that the workingmedium melts a fusible link and emits accordingly into the environment,causing the power transmission to be interrupted by theVottinger-circuit in turbo clutch 2.

The inventive operational method for drive train 1 is described belowwith the assistance of an example of a dynamic change of an operationalstate, or respectively a load state. In this case only the operationalstate changes in as far as a change occurs from a shut-off operationalstate into an operational state of starting. Any other dynamic change isanalogous so that, for the expert, this example for clarification of theinventive method is sufficient.

The illustration in FIG. 2 shows a simplified sequence for drive train1, in particular for turbo clutch 2 of drive train 1. On the basis of astart signal given from the outside a correlative processing occurs, forexample in the area of analysis device 8 that shows implementation ofthe logic steps. After a short waiting period for initiation, it isinitially verified in the process sequence whether an appropriatecooling period was observed following a possible shut off due toexceeding a predefined maximum temperature, before proceeding in theprocess sequence. After verification of the function of analysis device8, electric motor 3 is then started as primary drive unit 3. Then ashort waiting period follows for suppression of startup prior toproceeding with a verification of the plausibility of the temperaturesignal of measuring device 6. Subsequently, a verification of theminimum required starting temperature difference for the first fiveseconds occurs, followed by a determination of whether there is anominal operation or a startup or respectively a blockage. In the caseof a startup or respectively a blockage, a correction of the temperaturesignal occurs which is not as necessary in the nominal operation.Subsequently, the temperature is compared with a predetermined maximumtemperature, and the process sequence starts anew with a verification ofthe temperature signal in regard to plausibility if the temperaturevalue is below the predetermined maximum temperature. If this is not thecase, shutting off of the electric motor occurs, in other words anemergency shutdown of the system.

Subsequently, prior to a possible manually and/or automaticallyimplemented renewed start of drive train 1, or respectively of electricmotor 3, a verification of the cooling time following the possibleshutdown due to exceeding of the predetermined maximum temperature isagain conducted. Due to this verification of the cooling time andpossibly the delay of the renewed start it is achieved that, based onthe unavoidable starting temperature difference an emergency shutdownoccurs again immediately, since the current temperature value plus therequired starting temperature difference again exceeds the maximumtemperature.

The sequence is described and demonstrated in detail with the assistanceof FIGS. 3A to 3D, wherein for simplification of the illustration thefollowing abbreviations and formula have been predefined:

Temperatures:

-   -   l_(BTM)/ϑ_(BTM): analogous BTM-output (4 mA . . . 20 mA=0° C. .        . . 200° C.)    -   ϑ_(Umgeb): ambient temperature of the clutch    -   ϑ_(VTK): “true” (corrected) clutch temperature, indication also        to operator    -   Δϑ/Δt: temperature gradient (temperature rise), calculated        according to formula 1 (see below)    -   Δϑ_(Anfahr,min): required startup temperature difference, in        order to be able to start the working machine under the actual        current load    -   ϑ₁: max. operating temperature (ϑ_(B max)), at which the load        should be reduced    -   ϑ₂: temperature at which the load must be removed    -   ϑ₃: peak temperature (ϑ_(SP max)) that leads to shutting down of        the system

Times/Timer (time counter)

-   -   t_(Abschalt): timer, that is started on overheating (exceeding        ϑ₃)    -   t_(Kühl): required cooling time after overheating of clutch 2 in        order to be able to start it again is determined        transaction-related and subject to the current load    -   t_(Start): timer, that is started at the start of the electric        motor    -   t_(Überbrück): Startup suppression (for example until 300 l/min.        is exceeded). If upon logic output (START E-MOTOR) the electric        motor is not started immediately, that time has to be added.    -   t_(Anlauf): max. startup time of the system, calculated from        simulation and 10 s safety margin    -   t_(Block): timer, that is started upon recognition of        startup/blockage    -   t_(Rest): resting time during blockage until shutting off of        system    -   t._(nϑ1): timer that is started when exceeding ϑ₁    -   t_(nϑ2): timer, that is started when exceeding ϑ₂    -   t_(Überbrück): timer that is started for the first time during        the transition of startup/blockage to nominal operation and        simultaneous cooling

Marker:

-   -   M_(heiβ): marker, if system was shut off due to overheating (=1)

Formulas:

$\begin{matrix}{{{{{{\Delta\vartheta}/\Delta}\; t} = \frac{\vartheta_{{BTM},{t\; 2}} - \vartheta_{{BTM},{t\; 1}}}{t_{2} - t_{1}}};}{t_{2} = {t_{1} = {2s}}}} & {{Formula}\mspace{14mu} 1} \\{\vartheta_{VTK} = {\left( {{3 \cdot {{\Delta\vartheta}/\Delta}}\; t} \right) + {10K} + \vartheta_{BTM}}} & {{Formula}\mspace{14mu} 2} \\{\vartheta_{VTK} = {\left( {{1.5 \cdot {{\Delta\vartheta}/\Delta}}\; t} \right) + {5K} + \vartheta_{BTM}}} & {{Formula}\mspace{14mu} 3} \\{t_{Rest} = \frac{\vartheta_{3} - \vartheta_{VTK}}{{{\Delta\vartheta}/\Delta}\; t}} & {{Formula}\mspace{14mu} 4}\end{matrix}$

wherein: t₁: current point in time

-   -   ϑ_(BTM,t1): temperature at point in time t₁    -   t₂: 2s before current point in time    -   ϑ_(BTM,t2): temperature at point in time t₂

During the program sequence the following values are continuously loadedinto analysis device 8:

-   -   l_(BTM)ϑ_(BTM): analogous BTM-output at output device (4 mA . .        . 20 mA =0° C. . . . 200° C.)    -   ϑ_(Umgeb): Ambient temperature of clutch 2. If in specific        application situation, temperatures of below 0° C. are excluded,        this input can continuously be internally set in the program        at >0° C.    -   P_(Last): proportional current load of system. This value can be        calculated at site, for example via the motor current, or can be        input into the controller by the operating personnel as selector        switch (120%, 100%, 90%, 80%, 70%, 60%). This input is required        in order to adapt t_(Kühl) and Δϑ_(Anfahr,min) to the current        load conditions (see table below). If this gradation is not        desired, firm value P_(Last)=100% can be accepted.

Moreover, additional values are predetermined accordingly on the basisof size of drive train 1, or respectively the efficiencies of the turboclutch 2 that are to be transferred and are stored in the region ofanalysis device 8.

-   -   t_(Überbrück): Startup suppression (for example to a speed of        300 l/min. of exterior components).    -   t_(Anlauf): max. startup time of the system, calculated from        TurboSim plus 10 s safety margin    -   ϑ₁: max. operating temperature (ϑ_(B max)), at which the load        should be reduced        -   ϑ₁=95° C. with NBR seals (perbunan)        -   ϑ₁=120° C. with FPM seals (Viton) for VTK≤750        -   ϑ₁=105° C. with FPM seal (Viton) for>VTK 750    -   ϑ₂: temperature at which the load must be completely removed.        Meaningful gradation should hereby be selected between ϑ₁ and        ϑ₂.    -   ϑ₃: peak temperature (ϑ_(SP max)) that leads to shutting down of        the system        -   ϑ₃=ϑ_(SSS)−15° C.

Communication between analysis device 8 and electric motor 3 as theprimary drive machine is then typically very rudimentary, because only astart release or an immediate shutdown of electric motor 3 needs to becommunicated.

With reference to one exemplary possible design, FIGS. 3A to 3D providea detailed explanation of the sequence illustrated in the core of FIG. 2on the basis of the described abbreviations and values. Below, only afew points are discussed in order to provide a better understanding ofthe drawings.

Steps 1 to 9 are again illustrated in FIG. 3A. Overall, the operation ofdrive train 1 starts with a start order, whereupon after turning on ofthe power supply in step 1, marker M_(heiβ) is set to zero. In step 2 atime span of 10 seconds is observed before it is verified in step 3whether marker M_(heiβ) is set to zero, in other words if the startingprocedure has been initiated shortly before or not. If this is not thecase, step 3 is initiated typically via the region identified as D inthe manner that is explained later; and, previously a temperature basedshutoff of electric motor 3 occurred. In this case the shut-off timer iscompared with the cooling timer, wherein the shut-off timer is startedwith the temperature based shut-off and the cooling timer ispredetermined as a value in the manner described later.

Either a warning is issued that turbo clutch 2 is too hot and ideally, aresting period can be issued for the still required cooling. If thevalue of the shut-off timer is greater than the predetermined time valuet_(Kühl), then marker M_(heiβ) is set to zero and timer t_(Abschalt) isstopped and also set to zero. Step 3 is then restarted and, due tomarker M_(heiβ) having been set to zero, directly cycles through thefirst prompt. In step 4 the function of analysis device 8 is verified inthat the base current value of contactless thermal measuring device 6 isretrieved. If this is higher than the predefined threshold value,everything is ok. If not, an alarm is issued accordingly and an errormessage is generated.

Electric motor 3 is subsequently started and a response threshold timeis observed. In step 7 the plausibility of the temperature value ofmeasuring device 6 is verified in that information is retrieved as towhether the current delivered via measuring device 6 is within a certainrange. If this is the case, everything is ok. If this is not the case awarning is issued accordingly and electric motor 3 is again stopped. Ifthe ambient temperature is too low, there is a wait for warming of theclutch or respectively the turbo clutch.

In step 8 a verification of the minimum startup temperature differenceoccurs for the first five seconds. If the temperature reserve is too lowfor starting, electric motor 3 is again stopped and marker M_(heiβ) isset to 1. The system then returns to step 3. Otherwise a start occursand a calculation of the temperature gradient occurs via formula 1.

In step 9 it is evaluated whether the temperature gradient isaccordingly large or small, so that the events that are differentiatedas A and B in step 9 can be selected. These events are the nominaloperation (B) or respectively the operation during startup, or ablockage (A) as can be seen in the overview in the illustration in FIG.2.

In FIG. 3B the sequence according to A is more clearly specified withsteps 10, 11 and possibly 13. In step 10 it is again verified whetherthe temperature gradient exceeds a second threshold of 10 K/second. Ifthis is the case it is set to 10 K/second. If this is not the case,timer t_(Block) that otherwise would be started after the determinationis started immediately. Via a time request, whether the timer is belowor above 5 seconds a calculation of the temperature of the turbo clutchis performed, either according to formula 2 or formula 3.

In step 11 a related warning is issued in the case of a blockage and ifnecessary measures for removal of the blockage are initiated.Subsequently a rest period is calculated with formula 4 and a warning isissued, so that under the momentary conditions the shutdown occurs inthe value that was calculated by way of the resting period value.Subsequently, a verification occurs as to whether the temperature of theclutch has in fact exceeded the maximum temperature limit value ϑ₃. Ifthis is not the case, return to point C is between points 6 and 7occurs.

If this is the case, then electric motor 3 is shut off in step 13 andthe relevant timers are set according to the illustration in FIG. 3B.After output of an alarm we return to step 3, so that after a sufficientcooling a renewed start of electric motor 3 can occur.

In the illustration in FIG. 3C, monitoring for the nominal operation isdescribed. Here, essentially temperature monitoring occurs thatdifferentiates between lightly elevated temperature with the necessityto reduce the load, and a strongly elevated temperature with thenecessity to completely remove the load. Only if no appropriate measureoccurs, step 13 for stopping of electric motor 3 analogous to theillustration in FIG. 3D is activated; otherwise the sequence betweensteps 6 and 7 is restarted and continuously cycled through.

In order to determine the predefined time value t_(Kühl) the situationdescribed below is for example implemented, in particular subject to theload. This can occur for different load conditions and thus always leadsto different results. The method in the example in FIGS. 4 and 5 isexemplary only for the load of 100%.

Several individual curves can be seen in the diagram in FIG. 4. Forexample, the motor speed 10 and motor torque 11, as well as secondarytorque of turbo clutch 2 are illustrated. Moreover, recognizable in FIG.4 is a curve 13 of the load speed, as well as a curve 14 with the loadtorque. Decisive for the therein illustrated view is in particulartemperature progression 15 in turbo clutch 2. It can be seen that duringthe startup process the speed increases quickly from the left end of thediagram and the torque that is transferred to turbo clutch 2 alsoincreases until it levels off in the range of load torque 14 aftercompleted process. This start process or respectively start-up isindicated in the illustration in FIG. 4 with arrow 16 and lasts forexample 38 seconds.

At the same time, it can be observed that the temperature at the farleft in the diagram rises to a constant temperature value during regularoperation. This rise in temperature is indicated with arrow 17 andidentifies the required starting temperature Δϑ_(Anfahr, min). that, inthe illustrated design example amounts to 58 K. Additional values, forexample the ambient temperature of the turbo clutch and the startingtemperature of the turbo clutch during shut-off due to reaching themaximum temperature ϑ₃ are thereby included into the simulationillustrated in FIG. 4.

In an additional simulation in the illustration in FIG. 5 the cool-downbehavior of turbo clutch 2 can now be recognized. The curve of turboclutch 2 is again identified with reference 15 and the permissibleoperating temperature of turbo clutch 2 with the predefined load—in thiscase 100%—is identified with reference 18. Temperature curve 15 showsthe simulated cooling of turbo clutch 2 under the described conditions.The startup temperature difference Δϑ_(Anfahr, min) of 58K is againshown by arrow 17 which means that cooling by at least 58K compared tothe permissible temperature 18 of turbo clutch 2 has to have been atleast 58K in order to not provoke renewed overheating and shutoff orrespectively load reduction on turbo clutch 2 during startup. If thisvalue is entered into the diagram, a respective value results for therespective point on the temperature progression time axis that is alsoindicated by arrow 19. This is the predefined time value t_(Kühl) that,in this illustrated design example is 7000 seconds.

In the inventive method therefore, value t_(Kühl) is predefined with7000 seconds in step 3 of the sequence. This means that timert_(Abschalt) has had to have run already for 7000 seconds before arenewed start of electric motor 3 according to the provided logicdiagram becomes possible. Based on this specification, maximum uptime ofthe system is made possible, and starting attempts that lead againimmediately to a shut-off and thus ultimately to prolongation of theoverall duration during which the system is not available or notcompletely available can be prevented.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

What is claimed is:
 1. A method for operating a drive train, comprising:providing a primary drive machine; providing a working machine driven bythe primary drive machine; providing a hydrodynamic clutch between theprimary drive machine and the working machine; and providing atemperature detection device for detecting a temperature in thehydrodynamic clutch; detecting the temperature of the hydrodynamicclutch at the time of a change from at least one of a load state and anoperating state of the drive train to at least one of a new load stateand a new operating state of the drive train; calculating an expectedtemperature progression on the basis of the detected temperature and atleast one of the new load state and the new operational state of thedrive train; and issuing at least one of a warning signal and a stopsignal for the primary drive machine if a temperature of the calculatedtemperature progression exceeds a predetermined maximum temperaturewithin the expected duration of at least one of the new load state andthe new operational state.
 2. The method according to claim 1, whereinat least one of a warning signal and a stop signal for the primary drivemachine is issued if the current temperature becomes greater than itsrespective value in the calculated temperature progression.
 3. Themethod according to claim 1, wherein in the case of a change of theoperating state from a turned-on to a shut-off state of the primarydrive machine, based on the load state at the time of the shut-off,additionally a start-up temperature progression of a warm-up in the caseof a start-up of the drive train is calculated from which a maximumstart-up temperature difference is determined; wherein before release ofa new start of the drive train, a wait occurs until the calculatedtemperature progression has reached a release temperature that fallsbelow the maximum temperature by at least the startup temperature. 4.The method according to claim 3, wherein reaching the releasetemperature occurs by way of a comparison of the current detectedtemperature with the correlative value of the calculated temperatureprogression.
 5. The method according to claim 3, wherein reaching therelease temperature is monitored by a time counter; wherein uponshut-off, the time counter is started; wherein during a new start of theprimary drive machine it is first verified whether the time counter hasreached a time value at which the calculated temperature progressionreaches the release temperature.
 6. The method according to claim 3,wherein reaching the release temperature is monitored by a time counter;wherein upon shut-off, the time counter is started; wherein during a newstart of the primary drive machine it is first verified whether the timecounter has reached a time value that is referenced subject to at leastone of an ambient temperature, a temperature at the time when the drivetrain is shut off, and a load of the working machine in characteristiccurves or characteristic fields of at least one of previous measurementsand simulation values.
 7. The method according to claim 1, wherein whencalculating the temperature progression, the ambient temperature of thehydrodynamic clutch is considered.
 8. A method for operating a drivetrain, comprising: providing a primary drive machine; providing aworking machine driven by the primary drive machine; providing ahydrodynamic clutch between the primary drive machine and the workingmachine; and providing a temperature detection device for detecting atemperature in the hydrodynamic clutch: detecting the temperature of thehydrodynamic clutch at the time of a change from at least one of a loadstate and an operating state of the drive train to at least one of a newload state and a new operating state of the drive train; calculating anexpected temperature progression on the basis of the detectedtemperature and at least one of the new load state and the newoperational state of the drive train; and issuing at least one of awarning signal and a stop signal for the primary drive machine if atemperature of the calculated temperature progression exceeds apredetermined maximum temperature within the expected duration of atleast one of the new load state and the new operational state, whereinthe current temperature value that is detected by the temperaturedetection device is corrected with a temperature value, subject to theoccurring temperature gradients.
 9. The method according to claim 8,wherein the correction value is selected proportional to the temperaturegradient.
 10. A method for operating a drive train, comprising:providing a primary drive machine; providing a working machine driven bythe primary drive machine; providing a hydrodynamic clutch between theprimary drive machine and the working machine; and providing atemperature detection device for detecting a temperature in thehydrodynamic clutch: detecting the temperature of the hydrodynamicclutch at the time of a change from at least one of a load state and anoperating state of the drive train to at least one of a new load stateand a new operating state of the drive train; calculating an expectedtemperature progression on the basis of the detected temperature and atleast one of the new load state and the new operational state of thedrive train; and issuing at least one of a warning signal and a stopsignal for the primary drive machine if a temperature of the calculatedtemperature progression exceeds a predetermined maximum temperaturewithin the expected duration of at least one of the new load state andthe new operational state, wherein as of a maximum operatingtemperature, the load on the hydrodynamic clutch is reduced by adecrease in at least one of a drive power and a load, wherein a maximumoperating temperature is less than a maximum temperature.
 11. The methodaccording to claim 10, wherein with a warning temperature that ispredefined greater than the maximum operating temperature and lower thanthe maximum temperature, a complete reduction of the load occurs. 12.The method according to claim 1, wherein the hydrodynamic clutch isprotected by a fusible safety plug that is designed for a temperatureabove the maximum temperature.
 13. The method according to claim 1,wherein the measurement of a temperature of the hydrodynamic clutchoccurs via a measurement in the hydrodynamic clutch and a contactlesstransfer of a measured value into a stationary analysis unit.